I have the urge to be cuckolded so bad but how do I get my girlfriend/wife to want to proceed?

The first step is to finding out if she is interested in it or not.

Well, how would you do that?

Here are some way you can find out,

Start with the roleplay

The best time to bring the topic is during sex (and follow-up later), if she enjoys it she will be more vigorous in sex (and that's how you know she is at least excited about it).

Talking about MMF and help from erotica

Once in a while, talk to her about how will it be if there will be two-man(one is you) and it will be a threesome, you both can read or watch erotica and roleplay with it. You may also explore cuckolding in erotica (stories, visuals etc.)

Take it slow, don’t jump

MMF is always a good topic before you directly jump to cuckolding as talking directly about it might be a negative step. Some couples I have been with, they never talked about cuckolding or talked a little how the real situation will be (they had an idea of course) and they enjoy it rather experiencing it. But you need an experience Bull/Lover for this to work and someone who can guide you as a beginner couple.

Open communication

The more open you are with your partner, the more acceptance there will be and the more comfortable the situation gets. It helps in taking things in the right direction. So always talks things through.

Taking things at the next level

Once you both are mentally ready to at least try it, the next step is to find a suitable guy who understands cuckolding. This can be challenging but you will know if he really understands cuckolding after talking it for a while. Do not involve someone you already know (Friends/relatives etc.), it will complicate the situation for the long run.

Explore more and have fun with it

Once you are in this lifestyle and wanna explore more, there are absolutely no limit, but always talks things together.

Happy Cuckolding!